1. CHEMISTRY IS LARGELY A QUANTITATIVE SCIENCE
The recording of a quantitative observation (some kind of numerical value) in experiments involves ACCURACY and PRECISION. These are not the same thing.
It is necessary to record data with both the appropriate number of SIGNIFICANT DIGITS and the CORRECT UNITS.

2. Systems of measurements
A. English System - what the United States uses today derived from the 'Kings" feet (Old England)
Units
1 foot (“big feet")
1 inch (knuckle)
1 yard (King Henry I - nose to thumb)

3. System Internationale (S.I.)
The creation of the decimal Metric System at the time of the French Revolution and the creation of two platinum standards representing the meter and the kilogram was the first step in the development of the present International System of Units.

4. Prefixes

5. The seven fundamental units of measurement
Physical property
Name of unit
Symbol
Length
meter m
Mass
kilogram kg
Time
second s
Electrical current
ampere A
Temperature
Kelvin K
Luminous intensity
candela Cd
Amount of substance
mole
mol

6. Length
Length is a fundamental unit. In the metric system, the meter is a the standard unit for measuring length. It is a little longer than a yard.
The standard unit of metric length is kept in Paris. It is equal to inches. Since the meter is equal to 100 centimeters (cm), then 1 inch is equal to 2.54 cm.
Comparisons:
centimeter - width of your fingernail
kilometer miles
millimeter - thickness of a dime

7. Mass
Mass is a fundamental unit; it is a measure of the quantity of matter present. Although we typically use the words mass and weight interchangeably in normal conversation, mass and weight actually have different meanings. Weight includes the effect of gravity on mass. In a space capsule, your weight would be zero (absence of gravity) but your mass would be the same value as it was on earth. The standard unit of mass is the kilogram (kg).
Conversions factors:
1 pound = 454 g
2.2 pounds (lb) = 1 kilogram (kg)
1 gram (g) = 1000 milligrams (mg) or 1 mg = g
1 kilogram (kg) = 1000 grams (g) or 1 g = kg

8. Volume
– volume is a derived unit (using length units). It is a measure of space. In simple terms, it is a measure of three (3) length units in three dimensions (breadth, length and width). The standard unit of measurement is the meter cubed (m3) or the centimeter cubed (cm3).
In chemistry, volume is typically measured for a liquid. The standard unit of measurement for a liquid is the liter (L). The liter is similar to a quart in the English system.
Conversion factors:
1 liter (L) = 1.06 quarts (qt)
1 quart (qt) = liters (L)
1 liter (L) = 1000 milliliters (ml) or
1 milliliter (ml) = liter (L)
1 milliliter (ml) = 20 drops
At room temperature, 1 milliliter (ml) of water = 1 cm3. (or 1 CC)

9. Temperature A fundamental unit. There are three(3) temperature scales
BPH FPH2O Difference
(1) Fahrenheit (F) ° ° °
(2) Celsius (centigrade) (C) ° ° °
(3) Kelvin (K)
Conversion:
Kelvin to Celsius (K -> C) C = K - 273
Celsius to Kelvin (C -> K) K = C + 273
Celsius to Fahrenheit (C -> F)
i multiply C x 9/5
ii Add C x 9/5 + 32
Fahrenheit to Celsius (F -> C)
i add F - 32
ii multiply (F - 32) x 5/9

10. Derived units
Derived units can be resolved into combinations of fundamental units
Area and volume involve only the units of length
Most involve combinations of different units

11. Dimensions
It is important to keep track of the dimensions in derived units.
All the more when making conversions:
1 cm = 10 mm
1 cm2 = 100 mm2
1 cm3 = 1,000 mm3

12. Density Mass divided by volume Units are: g/cm3(solid) g/mL (liquid)
g/m3 (gas)

13. Density and temperature
In most cases, the density of a substance decreases with temperature. (Why is that?)
Water provides a critical exception to the rule

14. Conversion factors
Making conversions between different units is very important
Always keep track of the units
Make use of unit factors
There are 1000 mg in 1 g (conversion factor)
1000 mg/1 g = 1; 1 g/1000 mg = 1 (unit factors)
There are two unit factors for any conversion

15. Unit factors at work How many grams are there in 2680 mg of sucrose?
We know there are mg in 1 g
1 g/1000 mg = 1 (unit factor)
? g = amount in mg x unit factor
? g = 2680 mg x 1 g/1000 mg = g
Unit factor has value of 1 – no change in value
Application of unit factor causes old units to cancel
Never forget to show units of any measurement – unless it is a unit-less quantity